I have a funcsurface, and I recommend that you buy two or three ratpadz for the same price. The funcsurface is definitely better (I'm have both), but not enough to warrant the cost. The Ratpadz also wear out a little quicker from my experience. Buy some mouse skates, too. Slicker is better--you just have to get used to it.
Also, a lighter mouse will make your hand more agile. There is a weight in the MX500 that can be removed.
As long as you're careful, and have the mouse disconnected from the pc at the time, its quite safe to open up the mouse. Looking at the mouses bottom you should see some imprinted crosses on the labels. There'll be one in the middle of the bottom label, and either one cross to the right of the top label, or one either side of where the cable enters the mouse, depending on the revision of the mouse. These crosses are indicators of the screws holding the mouse together. With these screws out the top half of the mouse should seperate quite easily. You should then be able to see the large metal weight screwed into the top half of the mouse, held in with a single screw. Remove the weight, and carefully screw the two halves of the mouse together. Take the time to make sure all of the screws are in evenly, to avoid any 'rocking' of the mouse on the mousepad. You should then have a perfectly working, slightly lighter MX500.